I. Field of the Invention
This invention relates to air horns used to provide warning sounds over wide distances. More particular, the invention relates to air horn apparatus that is portable.
II. Background Art
Air horns are commonly used as warning devices because they are capapble of providing very loud and distinctive sounds that carry over large distances. For example, air horns are used in the mining and construction industry to provide warnings when blasting is about to take place.
A very common kind of portable air horn apparatus consists of an air horn attached to a valve device that can be fitted to the neck of a compressed gas canister. The valve device includes a trigger that, when operated, allows compressed gas from the canister to operate the air horn. Devices of this kind are relatively inexpensive and lightweight and can generate sound at a high volume. However, gas canisters contain a finite amount of compressed gas that allows only a few uses before the canister has to be changed. Even worse, the valve devices tend to allow leakage of the gas from the canisters, thus further reducing the number of uses of the device before replacement of the canister is necessary. Gas leakage can also lead costly or dangerous situations in which an apparatus is unexpectedly found to be inoperative due to leakage and necessary warnings cannot be given, at least until a new canister can be obtained. The unreliability of apparatus of this kind makes it unsuitable for professional use.
There is consequently a need for more reliable and effective apparatus of this kind.